1. Field of the Invention
This invention relates to an optical reading apparatus, and more particularly to an optical reading apparatus which can optically read information from both of two kinds of documents or the like: a document or the like in which information is born on an optically reflective body (hereinafter referred to as "a reflective original"); and a document or the like in which information is born on an optically transparent body (hereinafter referred to as "a transparent original").
2. Description of the Prior Art
In a conventional optical reading apparatus, as shown in FIG. 10, a reflective original 117 from which information is to be read is placed with the side to be read face down on top of a transparent glass table 116 of an original table. The apparatus of FIG. 10 comprises an optical reading unit 110 which includes a mirror 112, a lens 113, and a line CCD sensor 114. While illuminating the side to be read by a light source 111 and moving the glass table 116 by a pulse motor 115, light beams reflected from the original 117 are further reflected by the mirror 112 and then converged by the lens 113 to impinge on the line CCD sensor 114, thereby obtaining image signals corresponding to the information on the reflective original 117.
Originals from which information is to be read are not always reflective originals, but often transparent originals such as OHP films. When a transparent original is set onto a conventional optical reading apparatus for a reflective original, so as to read out information from the transparent original, all the light beams pass through the transparent original so that image signals representing black only are obtained. On the other hand, when a reflective original is set onto a conventional optical reading apparatus for a transparent original, light beams cannot pass through the reflective original, resulting in that information cannot be read from the reflective original. Optical reading apparatus which are capable of reading both reflective and transparent originals have been manufactured, but these are large in size and expensive.